Nintendo's throwing such a curveball, it's tough to say where they'll go. Considering their competition hasn't changed, and their market hasn't really changed except for lip service, I wouldn't be suprised if Nintendo was in 3rd again. Sony's brand is very, very strong, and combined with the most horsepower they might come out on top again if Blu-ray pulls through. X360 promises a lot, but even in the USA people are resistant to Microsoft's Green Machine.
Wii really needs to prove it's premise to pull ahead this time, though they've priced it so they don't need to "win" anything to remain profitable and stay afloat. If either Microsoft or Sony drop the ball, the scrawny and scrappy Nintendo will devour the weak, and make that lack their own strength.